干旱区生态环境知识资源中心

Meliaceae is a widely distributed subtropical and tropical angiosperm family. This family included approximately 50 genera encompassing 700 species, occurring in a variety of habitats, from rain forests and mangrove swamps to semi-deserts. As human actions increase and the climate changes, the growing environment of plants is changing and habitat destruction is threatening to erode the genetic resources of these species. Thus, the conservation of the genetic biodiversity has been widely recognized to be necessary. Cedrela and Toona are closely related genera. Although they have been indisputably considered independent genera, their genetic diversity and phylogenetics are still confused. In this study, the genetic diversity and phylogenetics of 17 Toona sinensis populations were determined based on the DNA sequences of regions of the chloroplast DNA (cpDNA) genes matK and rbcL and regions of the ribosomal DNA (rDNA) 5S gene and internal transcribed spacer (ITS) regions.

The rbcL region exhibited little genetic variation. The 5S region showed the highest level of genetic variation, however, phylogenetic trees based on this region bore no obvious relationship to the geographic origins. The monophyly of Cedrela and Toona was strongly supported by analyses of the matK regions whereas the ITS results only supported the monophyly of Cedrela. This conclusion was supported by representative variable sites within the ITS regions, which were identical in T. sinensis and Cedrela but differed from the other Toona species. This study contributed better molecular discrimination between Cedrela and Toona and among Toona species.